Photodynamic therapy (PDT) was first suggested as a method to treat malignant tumors. In this method, the subject is administered a photoactive agent such as a porphyrin derivative or a phthalocyanine; the photoactive agent was believed to localize preferentially in tumor tissue. When the tumor tissue was then irradiated with light of appropriate wavelength and absorbed by the photoactive agent, the decay of the photoactivated drug results in the regeneration of the drug and destruction or impairment of the surrounding tissue.
The use of PDT in the treatment of tumors has been established for many years, beginning with the use of hematoporphyrin derivative (HPD, a mixture of porphyrins) and a more potent derivative of HPD (porfimer sodium) which is described in, for example, U.S. Pat. No. 4,932,934. In addition to the treatment of tumors, PDT has been used to treat atherosclerotic plaques as described in U.S. Pat. No. 4,577,636 and in the treatment of skin diseases as described in U.S. Pat. No. 4,753,958. PDT has also been used to eradicate pathogens from blood and body fluids as described in U.S. Pat. No. 4,878,891 and U.S. Pat. No. 4,727,027.
A particularly useful group of photosensitizers, designated the "green porphyrins," is described, for example, in U.S. Pat. No. 5,171,749, incorporated herein by reference.
PDT has been found effective, generally, in destroying and impairing areas of neovascularization, as described in U.S. Pat. No. 5,770,619 without the necessity for the photoactive agent homing to a targeted area. This has particular application in treatment of diseases of the eye, in particular, age-related macular degeneration as described in U.S. Pat. No. 5,798,349. Photodynamic treatment of the eye has also been found to improve vision as described in U.S. Pat. No. 5,756,541. Photodynamic therapy has also been found useful in inactivating selectively certain white blood cells, as described in U.S. Pat. No. 5,776,966 and as further described in U.S. Pat. No. 5,807,881. Photodynamic therapy has also been found useful to treat rheumatoid arthritis when provided locally to affected joints, as disclosed in U.S. Pat. No. 5,368,841. Transplant rejection is also minimized using this technique, as described in U.S. Ser. No. 08/759,318, which is allowed.
All of the foregoing patent documents are incorporated herein by reference.
Thus, PDT has been found useful in a variety of contexts, including treatment of conditions which involve neovascularization, inflammation, and immune responses. However, it has not heretofore been realized that PDT can prevent as well as treat neovascularization. Thus, PDT has now been found, as a result of the present invention, to be useful for treatment of conditions associated with unwanted neovascularization at much earlier stages than would previously have been thought.